THz spectroscopy has been used to study a variety of physical phenomena ranging from atomic transitions to dynamics of biological molecules, and hence involves a wide range of disciplines including physics, chemistry, engineering, astronomy, biology, and medicine.
Terahertz (THz) frequency band lies between the microwave and mid-infrared region of the electromagnetic spectrum. Molecules having strong resonances in this frequency range are ideal for realizing Terahertz tags which can be easily incorporated into various materials. These THz tags find novel use in various counterfeiting applications such as detection of fake currency notes, security documents and counterfeit pharmaceutical drugs, brand protection, and labeling of consumer and industrial products/solutions. The absence of THz signatures for organic materials typically used in consumer/industrial labeling products also makes the present approach advantageous since the embedded THz tags can be easily detected.
THz spectroscopy of molecules, especially at frequencies below 10 THz provides valuable information on the low frequency vibrational modes, viz. intermolecular vibrational modes, intramolecular vibrational modes, hydrogen-bond stretching, torsional vibrations in several chemical and biological compounds. So far there have been very few attempts to engineer molecules which can demonstrate customizable resonances in the THz frequency region.
An article titled, “Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose” by Z.-P. Zheng et al. in Optics Communications 285 (2012) 1868-1871 reports the THz spectra of glucose and fructose in the frequency region from 0.5 to 4.0 THz by THz-TDS at room temperature and employs the gaseous-state theory to simulate the isolated molecules of glucose and fructose.
Another article titled, “Discrimination of Chiral Solids: A Terahertz Spectroscopic Investigation of L- and DL-Serine” by King et al. in J. Phys. Chem. A, 2010, 114, 2945-2953 reports THz absorption spectra from 10 to 90 cm−1 for L- and DL-serine along with a complete computational analysis by solid-state DFT using periodic boundary conditions.
Molecules having strong resonances in the THz frequency range are ideal for realizing Terahertz tags. These THz tags find novel use in various anti-counterfeiting applications such as detection of fake currency notes, security documents and counterfeit pharmaceutical drugs, brand protection, and labeling of consumer and industrial products/solutions.
However, there have been very few attempts to engineer molecules which can demonstrate customizable THz resonances. Hence, new molecules with unique and customizable spectroscopic signatures in the Terahertz region are required for incorporation as tags in various anti-counterfeiting applications (currency, pharmaceutical drugs, automotive parts, brand protection, and labeling of consumer and industrial products/solutions, etc.)